OBJECTIVETo study the clinicopathologic features of leiomyosarcoma with prominent osteoclast-like giant cells.

METHODSThe clinical and pathologic features of 7 cases of leiomyosarcoma with prominent osteoclast-like giant cells were analyzed. Immunohistochemical and ultrastructural studies were performed. The literature was reviewed.

RESULTSAll cases occurred in adults, with a mean age of 63 years. There was no significant sex predilection (male-to-female ratio = 4:3). The tumor involved subcutaneous soft tissue of thigh (number = 2), left back (number = 1), retroperitoneum (number = 1), small intestine (number = 1), breast (number = 1) and uterus (number = 1). Histologic examination showed that the tumor was composed of relatively uniform spindly cells arranged in interlacing fascicles. The hallmark was the presence of prominent osteoclast-like giant cells, either intimately admixed with the spindly cells (number = 6) or forming giant cell tumor-like nodules (number = 1). Immunohistochemically, the spindly cells expressed smooth muscle actin, muscle-specific actin, desmin and h-caldesmon in various degrees, whereas the osteoclast-like giant cells expressed CD68. Ultrastructural study showed smooth muscle differentiation in the spindly cells and histiocytic differentiation in the osteoclast-like giant cells. Follow-up data were available in 6 cases. There were local recurrences and/or metastases in all the 6 patients. Three patients were alive with unresectable or recurrent/metastatic disease and two patients died of the disease.

CONCLUSIONSLeiomyosarcoma with prominent osteoclast-like giant cells is a rare variant of leiomyosarcoma which should be distinguished from the so-called giant cell variant of malignant fibrous histiocytoma. The osteoclast-like giant cells are of histiocytic differentiation. Surgical resection remains the mainstay of management of this high-grade sarcoma.